The invention relates to an injection molding nozzle with at least one opening and a positively controlled closure element by which a communication opening of an injection mold can be closed.
Such an injection molding nozzle is known for example from DE 38 43 035 A1. The known injection molding nozzle includes, at the end of a supply channel for a plastic material melt, a discharge opening through which a closure needle extends. By means of the closure needle a discharge opening of an injection mold which is in communication with the injection molding nozzle can be closed. In this way, on one hand, the supply of plastic material melt through the discharge opening to the injection mold can be interrupted and, on the other hand, a backflow of plastic melt out of the injection mold can be prevented.
Such an injection molding nozzle is also described in DE 102 31 093 A1. This known injection molding nozzle includes two discharge openings which are oriented in opposite directions and through each of which a closure needle extends by which a communication opening of an injection mold can be closed. Each discharge opening is in communication with a supply channel for plastic material so that plastic material can flow through the discharge openings and be supplied to the communication opening of the injection molds.
For closing the mold communication openings, the closure needles of the known injection molding nozzles are axially moved so that they extend into the communication openings of the respective injection molds to sealingly close them. In order to obtain a fault-free surface of the injection molding part to be manufactured, it is necessary that the closure needles extend sufficiently far into the communication openings so that the tips of the closure needles are disposed in planar alignment with the surface of the respective injection molding part. This requires extensive adjustment work.
If the closure needle does not extend sufficiently far into the communication opening, that is, if the tip of the needle is disposed at a distance from the surface of the respective injection molding part, a small grafting is formed at the gate mark. If the closure needle extends into the communication opening beyond the surface for the respective molding part, the surface of the injection molding part may be scratched upon removal from the injection mold which renders the injection molding part unusable.
It is the object of the present invention to provide an injection molding nozzle by which a fault-free injection molding part can be produced without the need for time-consuming adjustment.